@Article{
Lau&Ornaghi:97c,
Author = "K.-K. Lau and M. Ornaghi",
Title = "The Relationship between Logic Programs and Specifications
         ---  The Subset Example Revisited",
Journal = "J. Logic Programming",
Volume = "30",
Number = "3",
Pages = "239-257", 
Month = "March",
Year = "1997"            }